Remarkable Stability Improvement with a High‐Performance PEALD‐IZO/IGZO Top‐Gate Thin‐Film Transistor via Modulating Dual‐Channel Effects

Abstract

Plasma‐enhanced atomic layer deposition (PEALD)‐based bilayer IZO (back channel)/IGZO top‐gate thin‐film transistors (TFTs) with different IZO and IGZO layer thicknesses are fabricated to evaluate the correlation between thickness and electrical characteristics/reliability caused by dual‐channel modulation. The dual‐channel formed by IZO stacked on the backchannel improves both mobility and reliability of devices as the IZO layer thickness increases. In the TCAD simulation, as the thickness of IZO increases, the current flowing through the IZO channel among the dual channels increases and the main channel transition from IGZO to IZO occurs above a certain IZO layer thickness. The main channel transition to IZO, which has high mobility and is located in the backchannel away from the gate insulator (GI), leads to a mobility increase with a lower threshold voltage (Vth) shift and a remarkable improvement of reliability deteriorated by the GI. As a result, PEALD‐based IZO/IGZO TG TFTs exhibit both high mobility (≈40 cm2 V−1 s−1) and high stability (ΔVth = ‐0.07 V) of a positive bias temperature stress up to 10 800 s. This suggests that ALD‐based dual‐channel regulation by nanoscale thickness control of the stacking oxide semiconductor can overcome the trade‐off between mobility and reliability.

Fatigue Effect of Stretchable a-InGaZnO TFT on PI/PDMS Substrate under Repetitive Uni/Biaxial Elongation Stress

“…using TMA and H 2 O. This can cause a negative V th shift by generating additional electrons in IGZO. − Figure (b) illustrates both the plausible mechanisms by which abnormal behavior can occur in positive gate bias.…”

Atomic layer deposition for nanoscale oxide semiconductor thin film transistors: review and outlook

“…In 2012, c-axis aligned crystalline IGZO (CAAC-IGZO) reported by the Semiconductor Energy Laboratory (SEL) exhibited high mobility (50 cm 2 V −1 s −1 ), extremely low off-current (∼10 −24 A µm −1 ) and enhanced bias stability, but it was necessary to increase the process temperature up to 800 • C [13]. A double active layer [14], back-channel treatment [15], and front-channel modulation [16] of TFTs were studied to optimize device properties. In addition to these studies, TFT structure optimization [17], interface engineering [18], post-treatment [19], and anion doping [20] were also investigated to improve the mobility and stability of oxide semiconductors.…”

“…With the growing interest in ALD, studies on materials using ALD have also rapidly increased, as shown in the table, which will be discussed in this review. In particular, superior electrical performances have been recently reported, including a remarkable mobility of over 100 cm 2 V −1 s −1 [43,46], an exceptionally low subthreshold swing under 100 mV/decade [64,66,80,83], and highly improved stability using a stack structure [14]. However, the main benefits of employing ALD for oxide semiconductor channel TFTs have not been clearly suggested.…”

Heterojunction oxide thin film transistors: a review of recent advances

“…They confirmed that efficient thickness control using ALD is a promising strategy for fabricating high-mobility and high-reliability heterojunction oxide TFTs. 56…”